High-frequency dielectric and conductometric properties of poly-l-lysine aqueous solutions at the crossover between semidilute and entangled regime
✍ Scribed by F. Bordi; C. Cametti; A. Motta
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 180 KB
- Volume
- 37
- Category
- Article
- ISSN
- 0887-6266
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✦ Synopsis
The dielectric and conductometric properties of poly-l-lysine aqueous solutions have been investigated in the frequency range from 1 MHz to 1.8 GHz, where micro-Brownian dynamics and internal motion of side-chain polar groups result in a well-defined relaxation process, intermediate between that caused by counterion polarization (characteristic of the polyelectrolyte nature of the polyion investigated) and that associated with the orientational polarization of the aqueous phase. The polymer concentration has been varied in a wide interval in order to investigate the influence of different chain conformations on the dielectric parameters as a consequence of the different concentration regimes occurring in these systems. With the help of polymer scaling theories, scaling relations for the dielectric strength and the relaxation time are presented, predicting, as the polymer concentration is increased, a transition from semidilute-unentangled to semidilute-entangled regimes. We compare these predictions with the experimental findings over the whole concentration range investigated, with a qualitative agreement. Deviations from the scaling behavior related to a crossover regime between unentangled and entangled regions are briefly discussed.